Hi Barry
Great stuff using a digester to produce gas to run an engine, my biggest problem would be finding enough compostable matter to get enough gas, there’s a few guys at work that fart a lot maybe I should hook em all to a manifold. LOL. If you can get a trailer load of chips from the council for 5 bucks that would be a good source of methane however the digestion will slow down considerably when it gets to the more fibrous wood chips that do not break down as easily when digested. There is an alternative though! By using up the easy to digest material up in the first process then pressing or drying out the water it would also make good fuel and gas producing material in a gas producer.
I have been able to secure 4 old large truck brake drums which are perfect for making a pressure vessel and fire box. All you need is to get one of them reverse machined with a good taper then bolt them back to back with large booker bar and nuts. Naturally you will need to make a threaded flanges one end and a block-off plate for the other end. As fire box a collar between both drums with a door fitted in it will work just fine.

I use all of my lawn cuttings in my composter as well as the kitchen scraps & produce about 200 litres of compost a year but I suspect that because the temperature in Karratha doesnt get much below 25C all year round I would be getting more than if I was down south when the southern winter sets in.

I know that it does produce a fair ammount of methane as I once for the sake of experiment sealed the lid on the plastic 44 gal drum I use & put a bubbler from my home brew in the lid & hey presto puffs of flame when I held a match to the bubbler as it was working.

What I suspect also is that as the material breaks down it possibly produces alcohol as would happen in a home brew kit if equal ammounts of waste feed & water where added at the same time; if I am right I could then put the liquid through a still & extract the wood alcohol for burning as well, that's my next step so I will just have to suck & see, I already have the still so there's no extra effort wasted if it doesnt work.

What I see in the long run is: I get methane to run the genny, compost for the garden, alcohol for burning (how is yet to be determined) & possibly the left over liquid may be high enough in nutrients for use as a fertaliser ?

Cheers
Barry

Edited by Barry T Coles on 09 April 2012 at 10:59am

__________________I need to learn from the mistakes of others.
I dont have the time to make them all myself.

Hi Barry
Yes I believe what you are doing is fine but I think the wood alcohol would be very minimal I think gasification of the digested material would be better because you would get Gas (for heating or engine) charcoal (for burning and filtering) and ash (for fertiliser and cement)
Regards
GYRO

I found out something I didn't know yesterday, there is a engine rev limit with producer gas. The gas mix combusts relatively slowly, so 2000 rpm is the top end. That pretty much rules out a two pole generator as a power source with straight wood gas as it needs 3000 or 3600 to match mains power Hz.

I guess the choices are 4 pole alternator at 1500rpm or a welder and inverter.

If it is not direct drive it all starts to get complicated. The cheapy one bearing alternator with the taper fitting is not really suitable for anything but direct coupling.
The question of horsepower is a good one, I have no idea.

I did find this on the gasification Australia website, gave me a chuckle

According to a 1946 issue of Power Farming in Australia, as many as 72,000 vehicles were retro fitted with gasifiers during wartime petrol rationing in Australia, and charcoal production to supply them reached an estimated 20,000 tons per month. [Note: according to some who recall this time directly, many of these gasifiers weren't in operation, but merely a cover for running cars on illegally-obtained motor spirit, power kerosene or turpentine!]
The automotive charcoal gasifier was by all accounts a technology of last resort for the petrol-staved motorist. Loading charcoal was a dirty business requiring a change of clothes; starting up the engine took took several minutes at the very least- often involving hand cranking a blower; hot ash carelessly dumped at the roadside caused bush fires; charcoal was often supplied wet and would not light, or was of such poor quality that the mineral matter melted and formed clinker inside the gasifier resulting in premature shut-down. The power developed by the engine was as much as 50% less on producer gas than on petrol; consequently going uphill was a very slow process.

Again in my researching on the net I came across a method of making your own charcoal. It consisted of a 44 gallon metal drum laying on its side. It had a pipe that came out of the top, ran to the back of the drum, down the back of the drum, and then along underneath the drum. The pipe that ran underneath the drum had holes in its side like a gas burner (which it was). This drum was then put on top of a fire box and was made so that it could be fulled encased. Wood was loaded into the drum from the front. The front was then blocked off, encasing the whole drum. A fire was lit underneath in the fire box and this baked the wood. Volatile gases were expelled from the baking wood, went up, down, and underneath the drum in the pipe system where the gases were ignited by the fire. This added extra heat to the drum and it became a self continuing system. The baking went on until no more gases were produced.
When everything cooled down again, the now charcoaled wood was removed for later use. Incomplete charcoaled wood was used as the fire material for the next load.
With regards to the charcoal during ww2, my dad told me that the best charcoal came from slowly converted timber. It was made by burying a stack of wood and then setting it on fire. A valve/door regulated air intake and it burned for a couple of days. When things cooled down, the stack was uncovered and it was then that you discovered if you had ashes or charcoal.
Hope this was confusing enough for all :)

When I was a kid I saw the big coke ovens at a steelworks. They said that they burn coal in the ovens until it becomes coking coal then it will burn hotter when they throw it in the furnace. That made no sense to me at the time, it seemed impossible.

I have been taught since that burning timber is a complex sequence of hundreds of chemical reactions that soak up heat in the fraction of a second before the two big reactions that generate heat.

( Hydrogen + oxygen = water and carbon + oxygen = CO2)

Making charcoal does two things it gets some of the energy hungry reactions over with so they don't slow the main reactions down and it increases the surface area with all the little pores so more Oxygen can get involved, gives us a faster burn.

oil and gas is a very similar process, plant material heated with no oxygen making big long stable molecules into short highly reactive ones, so we are many steps down the road of burning the wood without actually burning it.

these links from zen backpacking stoves are brilliant, I found them when I was trying to find something to replace power kerosine to run an old tractor.

When I was a kid I saw the big coke ovens at a steelworks. They said that they burn coal in the ovens until it becomes coking coal then it will burn hotter when they throw it in the furnace. That made no sense to me at the time, it seemed impossible.

When I was a kid my foster father worked as a stocker at SAGASCO the S.A. gas co; they cooked coal in furnaces and captured the gas as it come off in the process, the coke that was left over was sold to the public for home heating & it did burn very hot & visually clean, you could not see any smoke from the chimney when it was being burnt, it also left very little ash in the pan, the old man would then use the ash with something else & use it as a type of cement.

Those were the days when you got every little bit of use out of everything around you, I remember the Garbo only came once a fortnight & our bin was only ever 1/2 full, every thing useful was used around the home.

We were more economical with our use back before the throw away days we are now in.

Cheers
Barry

__________________I need to learn from the mistakes of others.
I dont have the time to make them all myself.

Hi Barry
Yes it is a shame people nowadays tend to just throw things out. My green waste bin is never put out and occasionally I pinch what is in the neighbours bin for my compost. Our recycle bin is full every fortnight and our rubbish bin gets put out about once a month half full. I am heavily into recycling and will be going back to America on 28th to help set up a truck tyre recycling facility at Pilot Mountain North Carolina. Currently I am negotiating the gasification of wood chip waste from office furniture manufacturer so along with everything else going on there are not enough hours in my day.

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